将其他参数传递给gtk函数

Question

我正在尝试学习如何使用gtk + 3.0制作GUI.我想将一个简单的参数,一个整数传递给一个回调函数,这样当我按下按钮时,参数的值会发生变化.这是我的代码:

#include <gtk/gtk.h>

void buttonFunction(GtkWidget * widget, gpointer data, int & n){
    n = 1;
}

int main(int argc, char ** argv){
    int n = 0;
    GtkWidget * window;
    GtkWidget * button; 

    gtk_init(&argc,&argv);

    window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    button = gtk_button_new_with_label("Osss");

    gtk_container_add(GTK_CONTAINER(window),button);
    gtk_widget_show_all(window);

    g_signal_connect(G_OBJECT(window), "destroy",G_CALLBACK(gtk_main_quit), NULL);
    g_signal_connect(G_OBJECT(button), "clicked", G_CALLBACK(buttonFunction), n);

    gtk_main();

    return 0;
}

我发现传递参数的唯一方法是作为指针:

void buttonFunction(GtkWidget * widget, gpointer * data);
g_signal_connect(G_OBJECT(button), "clicked", G_CALLBACK(buttonFunction), &n);

我如何通过这种方式传递多个参数？

Answer 1

有一堆有用的宏可以将整数（32 位，不再！）存储到指针中。

int a = 42;
gpointer ptr = GINT_TO_POINTER (a)
//GUINT_TO_POINTER (a), GBOOLEAN_TO_POINTER (a), GSIZE_TO_POINTER (a)

逆转：

int a2 = GPOINTER_TO_INT (ptr);
//GPOINTER_TO_UINT (ptr), GPOINTER_TO_...

Answer 2

要传递多个参数,您可以定义一个结构,填充它,并将指针作为gpointer user_data参数传递给结构g_signal_connect,这是最后一个参数.然后在回调中,您只需将user_data参数转换为指向结构的指针.

int main (int argc, char **argv)
{
    int n = 0;
    GtkWidget *window;
    GtkWidget *button; 

    gtk_init (&argc,&argv);

    window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
    button = gtk_button_new_with_label ("Osss");

    gtk_container_add (GTK_CONTAINER(window), button);
    gtk_widget_show_all (window);

    g_signal_connect(G_OBJECT(window), "destroy", G_CALLBACK(gtk_main_quit), NULL);

    /* Here's the magic: you pass a pointer to the variable you'd like to modify
     * in the callback, be it a simple variable or a struct */
    g_signal_connect(G_OBJECT(button), "clicked", G_CALLBACK(buttonFunction), &n);

    gtk_main();

    return 0;
}

void on_button_clicked (GtkButton *button, gpointer user_data) /* No extra parameter here ! */
{
    /* you cast to the type of what you passed as last argument of g_signal_connect */ 
    int *pn = user_data; 
    *pn = 1;
}

你必须使用文档中定义的回调签名(查看GtkButton文档的"信号"部分),你无法搞清楚.顺便说一句,你不能n作为参考而不是指针传递.如果你想在C++中使用GTK,请看看GTKmm.